The present invention will be defined by reference to the Clancy method of knee surgery but it is to be understood that the operation or an analagous operation may be performed on similar joints on humans and on other animals.
The cruciate ligaments form the intra-articular ligaments that stretch between the tibia and femur. The cruciate ligaments are strong, rounded bands which cross each other between their attachments, and are distinguished as the anterior and posterior cruciate ligaments. The anterior cruciate ligament extends obliquely upwards and backwards from the non-articular area in front of the intercondylar notch of the tibia to the back part of the medial side of the lateral femoral condyle.
The cruciate ligaments are vulnerable to extensive damage. The ligaments are prone to "tearing" rendering them incapable of performing their normal function, and this frequently occurs as a result of a sporting injury. Consequently, the ligaments need to be surgically replaced so as to prevent antero-posterior displacement of the tibia and to limit medial rotation of the tibia and lateral rotation of the femur.
It has been found that a suitable replacement for the cruciate ligament is the patellar tendon. The patellar tendon has the following characteristics and properties which enable it to best perform the role of the cruciate ligament: the patellar tendon
has excellent tensile strength;
is easily accessible;
is the proper length;
remains viable since it can carry its own blood supply from the infrapatellar fat pad;
both ends have a boney attachment to secure the graft.
Clancy and Associates have described a method of replacing a torn or damaged cruciate ligament with a patellar tendon. This method involves using a central strip of the patellar tendon based on a vascular pedicle from the infrapatellar fat pad. The success of the Clancy method depends on careful technical execution and precise placement of drill holes and a sound fixation of the contiguous bone blocks at each end of the graft. Previously, harvesting of the contiguous bone block was performed with power tools such as air driven saws and osteotomes to produce a strip of bone approximately 3 cm long 10 mm wide with a depth of 5 mm. The bone has on its flat surface the superficial fibers of the patellar tendon. This approximately triangular piece of bone is placed into a drilled tunnel in the femur and tibia respectively and fixed with sutures tied over a button placed at the mouth of the exiting tunnel.
There are disadvantages associated with the Clancy's procedure:
1. A triangular bone block fits poorly in the tunnel.
2. The fixation threads or button may break.
3. The bone block may break or patella may be fractured during havesting of the bone block leading to inferior fixation.
4. Incongruous fit of bone graft means there is a lesser chance of a good boney union in the tunnel graft interface.
The present invention is directed towards obviating some of the aforementioned problems associated with the Clancy procedure.